Modern high-performance lasers are used for the working of materials in industrial manufacture. Portal systems and robotic systems allow the user a maximally flexible guiding of the laser radiation to the workpiece. If the laser energy can be guided in light wave conductors to the working site, the dynamics of these systems is considerably increased. In order to insure body and life, passively acting (absorbing) protective walls, usually of metal, with simple plates or with plates arranged multiply in series are constructed around the laser area, the so-called enclosures. Laser radiation occurs with an extremely high energy density within these protective walls.
Additionally, uncontrolled reflections occur due to the working of the workpieces. Direct or indirect laser radiation, in the worst case the raw beam, strikes the enclosure, which for its part has the task of protecting persons outside from the radiation. Depending on the operating type of the laser system, this protection must be ensured for a time t, e.g., until the operator of the system notices the error and can stop it. As a result of the high energy and the often small distances to the protective wall, this time t until shut-off becomes less and less, or the requirements for the material of the enclosure become more and more demanding. Exclusively passive protective walls are therefore only conditionally suitable for securing persons.
The patent publications DE 100 17 284 C1, DE 103 25 906 A 1, DE 196 29 037 C1 only concern the passive protection by different embodiments of the surface qualities or of the intermediate spaces of the walls. The different thermal conductivity properties or the reflection capacity are used for realizing the passive radiation security. However, in practice the surfaces of the protective walls have already been contaminated after a short time by oil, dirt and dust so that the original properties of the protective devices are no longer given.
DE 36 38 874 C2 describes an active method wherein the inner wall facing the laser is provided like a safety fuse with an electrically active conductor. In contrast to the arrangement described here, a secure function is only given if the inner wall is exactly coordinated with the laser wavelength in its absorption behavior and in addition contains an electrically active safety device.
In order to be able to use this system, e.g., for fiber lasers with a very small diameter, the electrical conductor must be embedded in the wall with very narrow meanderings, which means a high constructive expense and a cost-intensive expense.
DE 89 08 806 describes an arrangement almost identical to the one described above.
DE 199 40 4 76 A 1 describes an active arrangement for recognizing optical radiation by any sensors. However, in this method the design of the protective wall is an essential component of the function. The using of thermal sensors on the wall facing the laser requires, depending on the thermal conductivity properties of the wall material, a not inconsiderable number of sensors for a secure shut-off. The described variant with optical sensors and a perforated sheet wall provided with a sheet inside again requires specially constructed wall elements.
EP-B-0 321 965 teaches an arrangement and a method for detecting a laser radiation exiting from a work area. To this end the work area is surrounded by a wall in which a detector is arranged which measures the illumination generated by laser radiation striking the wall. In order to check the sensor a photoemitter is arranged in a housing surrounding the recess whose radiation is received by the receiver for checking its function.
A safety system for checking laser beams can be gathered from GB-A-2 171 513. Here the laser beam is detected by a receiver. In order to check the good functioning of the receiver, an infrared light source is provided whose radiation is detected by the receiver.
DE 10 2006 026 555 A1 teaches a method for the detection of optical radiation such as laser radiation in a defined partial volume of a protective enclosure. Upon a penetration of the laser beam, signals are activated for turning the laser off.
EP 1 746 334 B1 teaches a protective wall for lasers for screening off a laser area.
Sensors are arranged in the wall which react to “hotspots” on the inner wall and accordingly make output signals available for turning off a laser beam.
Both publications have in common the fact that light sources for the emitting of a test beam for the self-monitoring necessary for this safety technology (function testing of the sensors) are also present in the interior of the wall volume to be monitored.
DE 10 2008 016 856 A1 teaches a beam protection element in which sensors detect the penetration of light of an external reference radiation source located externally in the cabin after penetration of the casing of the beam protection element and make appropriate signals available for turning off the laser. A self-monitoring of the sensors is not given.
The invention is based on the problem of using optical sensory technology in particular for active laser protection walls or for beam protection elements, wherein their ability to function is to be checked without an active optical testing with light sources or beam sources having to be used inside the volume to be optically monitored.
In particular, alternative, active laser protection wall sensors, active laser protection walls, active laser protection wall elements (and also their front-part variants in front of a passive protection wall) and active laser protection cabins should result as applications.